The present disclosure relates generally to the deposition of a nitride film on a wafer, and more particularly to deposition of a nitride film on a wafer by mixing cycles of plasma-enhanced atomic layer deposition processes and thermal atomic layer deposition processes.
As device and features size continue to shrink in the semiconductor industry, and also as 3-D device structures become more prevalent in integrated circuit (IC) design, the capability of depositing thin conformal films (films of material having a uniform thickness relative to the shape of the underlying structure, even if non-planar) will continue to gain importance. Atomic layer deposition (ALD) is a film forming technique which is well-suited to the deposition of conformal films due to the fact that a single cycle of ALD only deposits a single thin layer of material, the thickness being limited by the amount of one or more precursor reactants which may adsorb onto the wafer surface (i.e., forming an adsorption-limited layer) prior to the film-forming chemical reaction itself. Multiple “ALD cycles” may then be used to build up a film of the desired thickness, and since each layer is thin and conformal, the resulting film substantially conforms to the shape of the underlying device structure.
Semiconductor device fabrication may involve deposition of nitride films. For example, silicon nitride thin films have unique physical, chemical, and mechanical properties and thus are used in a variety of applications. For example, silicon nitride films may be used in diffusion barriers, gate insulators, sidewall spacers, encapsulation layers, strained films in transistors, and the like. Due to the role of silicon nitride films in IC design, it is often desirable for silicon nitride films to have a low wet etch rate or a low dry etch rate. Yet, the formation of such etch-resistant silicon nitride films via ALD has been difficult to achieve within typical thermal budget constraints.